5oo 



NEW YORK STATE MUSEUM 



dove-colored limestone of Yalcour island, and of the neighborhood 

 of Chazy. 



Observations. This form is in amount of curvature of the 

 shell, rate of growth, depth of chambers and character and position 

 of siphuncle, sufficiently similar to Hall's evasive species O. sub- 

 arc u a t u m that I should have identified it with the same if the 

 latter were not described by Hall and Billings as being sharply 

 annulated. 



/ 



Fig. 53 Fig. 54 Fig. 55 



Fig. 5 1 Ooceras (?) perkinsi sp. now Longitudinal section 



of the type. Natural size 

 Fig. 54 Ooceras (?) perkinsi sp. now Transverse section 



of the type, x T 9 P 



Fig. 55 Ooceras (?) perkinsi sp. now Enlargement (x 2.7) of 

 siphuncle to show the endosiphotube and sections of vertical lamellae 



From L o x o c e r a s 111 o 11 i 1 i f o r 111 c it can be distin- 

 guished by its curvature and the relatively smaller size of the 

 siphuncle. L . c ha m p 1 a i u e 11 s e has considerably shallower 

 chambers. 



Family oncoceratidae 

 Genus cyclostomiceras Hyatt 

 This new genus is proposed in Zittel-Eastman's textbook and 

 based upon the species described next as genotype. Its diagnosis is : 

 Slender, short, exogastric orthoceracones and cyrtoceracones, cir- 



